The extraction of hydrocarbons can be enhanced through the heating of shale oil, heavy oil, oil sand, or carbonate rock reservoirs with electromagnetic (EM) radiation in the radio frequency (RF) range. This is normally called “RF heating” and is generally implemented using a radiating element, located in the reservoir, to radiate an electromagnetic RF field (i.e. modulated at frequencies between 10 kHz to 100 MHz) into the reservoir. RF heating can typically allow for deeper and faster heat penetration than known steam-assisted technologies and can be implemented with simpler surface infrastructure. In addition, RF heating technology can potentially provide improved energy efficiently since it is an all-electrical operation and uses less energy than steam technologies.
However, known RF heating techniques are not well suited to the scenarios where the radiating element is separated from the RF power generator by a considerable distance, which may be due to the depth of the well, or where the well is horizontal and is 200 meters long or more. The long distance and limited diameter of the well, which in turn limits the available cross-section size of the transmission lines carrying the RF power to the radiating element, may lead to considerable loss of RF power before it reaches the radiating element. Further, the limited diameter of the well, and hence of the transmission lines, limits the available maximum RF power that can be transmitted down-hole. This makes it very difficult, if not impossible, to deliver to the radiating element a substantial amount of RF power, necessary for the extraction of the hydrocarbons using RF heating.